Digital signal processing is used to process data from a sensor, such as an acoustic transducer. Digital signal processing typically requires a large number of mathematical operations to be performed quickly and repetitively on a set of data. As illustrated in FIG. 1A, sound source 112 generates sound waves or acoustic object 113, which are received by transducer 104 that converts sound waves 113 to analog voltage signals 105. Analog-to-digital converter (ADC) or front-end circuit 102 then converts analog voltage signals 105 to digital signals 103, which are manipulated digitally in digital signal processor (DSP) 114 to output digital signals 107. Then, digital-to-analog converter (DAC) 116 converts digital signals 107 to analog signals 109.
Conventional acoustic sensor 100 includes transducer 104, front-end circuit 102, as illustrated in FIG. 1B. Front-end circuit 102 converts analog signals 105 into digital signals 103. Front-end circuit 102 typically includes an analog-to-digital converter (ADC) 110. Front-end circuit 102 may also include preamplifier 106 and lowpass filter 108. DSP 114 receives and processes digital signals 103, and then converts digital signals 103 into analog signals 107, as illustrated in FIG. 1A.
To reduce the power consumption of front-end circuit 102, a duty cycling method may be used to periodically shut off front-end circuit 102. The disadvantage of this duty cycling method is that the acoustic sensor 100 may miss important signals.
Another approach to reducing power consumption uses a wake-up circuit to detect the energy distribution of analog signal 105 in time domain, either shutting off front-end circuit 102 or waking it up based upon comparison of the detectable energy against a threshold. However, this approach may wake up front-end circuit 102 even when a desired sound signal is not present. Furthermore, when processing sound signals, front-end circuit 102 uses constant performance parameters and thereby uses power unnecessarily.
A third approach uses DSP 114 to identify frequency characteristics of sound signal or acoustic object 113 and to scale the power consumption of the front-end circuit 102 as needed based upon the frequency characteristics. Referring to FIG. 1A again, conventional acoustic sensor 100 may digitize analog signals 105 to generate digital signal 103, and then may use DSP 114 to compute occurrences of acoustic object 113. Digital signal 107 from DSP 114 converts into analog control signal 111 by digital-to-analog convert (DAC) 116 to adjust front-end circuit 102. This approach requires constant use of front-end circuit 102, DSP 114 and DAC 116, having significant power consumption, hardware complexity and latency.